Process of producing arsenate of lime



Patented July 13, 1926.

UNITED srArEs PATENT OFFICE.

FLORENTIN IBIDAUD, OF RHONE, FRANCE, ASSIGNOR TO SOCIETECHIMIQUE ISES USINES DU RHONE, OF PARIS, FRANCE; A CORPORATION OF FRANCE.

PROCESS .OF PRODUCING ARSENATE OF LIME.

. 1T0 Drawing. Application filed January It is known that calcium arsenite when heated in an OXldlZlng atmosphere, is transformed into calcium arsenate. Thls operation is usually carried on in an appropriate 5 furnace where the arsenite is heated, either.

indirectly through the walls of the furnace or directly by contact with oxidizing gases of high temperature.

The, present inventlon is based on the observation that it is not necessary, for this.

reaction, to utilize exterior heat, as is the case in all the processes heretofore known, but that the heat generated in the materials is sufiicient to bring about the oxidation.

' By selecting a suitable method of procedure, the arsenite can be oxidized by the use of-cold oxidizing gases, it being sufficient merely to induce the reaction by reliminarily carryin the mass to the oxldizing 29 temperature. wing to this extremely economical method of oxidizing, the technical possibilities. of this process are numerous."

A single example, without limitation, is given below: a The calcium arsenite is charged into a vertical furnace ,which has been carefully thermally insulated. The reaction is then induced by bringing apart of the charge to the oxidizing temperature, say approxi- IO mately' 450 0., any suitable means being em-' ployed for this purpose.

- From this moment all exterior heating becomes useless and is therefore discontinued. It is sufiicient' to cause a current of cold 0 gases to pass through the mass. The oxidation automatically continues by means ofthe heat generated, up to the complete transformation of the arsenite into arsenate; 1

19 One 'canoxidize in a furnace such as that referred to, an unlimitedquantity of arsenite carrying of! by suitable means the arsenate formed at the lower part and charging in proportion the corresponding uantlties of arsenite at the upper part, w 'ch' can. be

done continuously or intermittently. It is ve the operation of the furnace. If the temperature falls, the reaction will be arrested; if, onthe contrary, the temperature is too high the uality of the final product is-im paired.v he regulation ofthe temperature important to be able to regulate 15, 1926. Serial no. 81,591.

may be accomplished by any of the follow-. -1ng means.

By employing gas more or less rich in oxygen. Pure oxygen, or a. mixture of oxy gen and-air, or pure air, or, a mixture of air and neutral gases, may be used for this purpose. i

By using'arsenite in a more or less humid t0 condition, whereby the Water in evaporating will absorb more or less of the heat of the reaction. 7

The more or less humid calcium arsenite may be mixed, either with calcium arsenate already formed, or with slaked lime, or with limestone. The dehydration of the slaked lime or the decarbonation ofthe. limestone will absorb a part of the heat of reaction. One may obtain by these two last 7 means an arsenate mixture of lime, but that is unimportant, because the product generally used in agriculture is always diluted with lime.

It is understood that all these means of 7 regulation may be usedalone or simultaneously depending-on the combinations desired. I K

' Having thus described my invention, what I claim is:

1. A process ofxproducmg calcium .arsenate in a continuous way, which consists in charging in a" continuous way calcium arsenite into a furnace, heating a part of the starting charge to the oxidizing tempera ture, dlscontinuing'the heating as soon asthe reaction commences and causing a cur-- rent of oxidizing gases to pass through the progressing mass, and regulating the temperature to an amount necessary and suflicient for a complete oxidation.

2. In the process of produc' calcium arsenate in a continuous way, y oxidizing calcium arsenite, the heating being discontinued as soon as the reaction commences, 9 regulating the temperature produced by the reaction by insulating thermally the furnace and by introducing 1n the furnace heat absorbing substances. Y

3. In the process of producin calcium ar-' senate in a continuous way, by oxidizing calcium arsenite, the heating being discontinued as soon as the reaction commences, regulating the temperature produced by the reaction by adding to the arsenite a comregulating the temperature produced by the pound of lime able to give quick lime at reaction by adding to the arsenitc carbonate the oxidation temperature of the arsenite. of lime. 4. In the process of producing calcium ar- In testimony whereof I have signed my 5 senate in a continuous way, by oxidizing name to this specification.

calcium arsenite, the heating being discontinued as soon as the reaction commences, FLDRENTIN BIDAUD. 

